Epididymal epithelial degeneration and lipid metabolism impairment account for male infertility in occludin knockout mice

• Published in: Frontiers in endocrinology (Lausanne) Vol. 13; p. 1069319
• Main Authors: Liu, Bao Ying, Zhang, Bao Li, Gao, Da Yuan, Li, Qing, Xu, Xin Yu, Shum, Winnie
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 28.11.2022
• Subjects: Animals; arachidonic acid; Arachidonic Acids - metabolism; Endocrinology; epididymis; Epididymis - metabolism; Infertility, Male - genetics; Lipid Metabolism; luminal acidification; Male; Mice; Mice, Knockout; occludin; Occludin - genetics; Occludin - metabolism; Semen; Sperm Motility - genetics; V-ATPase; arachidonic acid; luminal acidification; occludin; V-ATPase; epididymis; lipid metabolism
• ISSN: 1664-2392; 1664-2392
• DOI: 10.3389/fendo.2022.1069319

Occludin (OCLN) is a tight junction protein and Ocln deletion mutation causes male infertility in mice. However, the role of OCLN in male reproductive system remains unknown. In this study, we used an interdisciplinary approach to elucidate the underlying mechanism of male infertility in related to OCLN function, including knockout mice as well as a combined omics analysis and immunofluorescent labelling. Our results showed that the epididymis of -null mice displayed a phenomenon resembling epididymal sperm granuloma, which occurred especially in the junctional region between caput and corpus epididymidis. Sperm motility and fertilisation capacity were also impaired in these -null mice, accompanied by enlarged tubules in the proximal regions and degeneration in the distal regions of epididymis. Cellular localization analysis showed that OCLN immunofluorescence was enriched only in the apical junction of epithelial principal cells in the proximal regions of epididymis. Integrative omics analysis revealed the downregulation of gene clusters enriched in acid secretion and fatty acid metabolism in the -null epididymis, especially the enzymes related to the unsaturated arachidonic acid pathway. The number of proton-pump V-ATPase-expression clear cells, a key player of luminal acidification in the epididymis, declined drastically from prepubertal age before sperm arrival but not in the early postnatal age. This was accompanied by programmed cell death of clear cells and increased pH in the epididymal fluid of OCLN-deficient mice. The lipidomics results showed significantly increased levels of specific DAGs conjugated to unsaturated fatty acids in the Ocln-mutant. Immunofluorescent labelling showed that the arachidonic acid converting enzyme PTGDS and phospholipase PLA2g12a were prominently altered in the principal cells and luminal contents of the -mutant epididymis. Whereas the carboxylate ester lipase CES1, originally enriched in the WT basal cells, was found upregulated in the -mutant principal cells. Overall, this study demonstrates that OCLN is essential for maintaining caput-to-corpus epithelial integrity, survival of acid-secreting clear cells, and unsaturated fatty acid catabolism in the mouse epididymis, thereby ensuring sperm maturation and male fertility.